This invention relates generally to water feed and distribution systems and, specifically, to a water leakage position estimating system and method for water feed and distribution systems.
A typical conventional method, which is put into practical use for estimating the position of water leakage of underground water main pipes or conduits, employs a sound pick-up rod. In this method, a sound pick-up rod is placed against the ground where the conduit is buried or is directly brought into contact with the buried conduit through a bore hole to detect vibrations caused by the water leakage. Vibrations picked up by and transmitted from the sound pick-up rod are mechanically or electrically amplified, and the position of water leakage is estimated by an inspector listening to the amplified vibrations through headphones. However, with this method, it is necessary to depend on the special skills of an experienced worker who can distinguish the magnitude of the sounds and slight differences in sound tone.
A device, which has been put into practice in an effort to automate the water leakage position detecting process, is the correlation type water leakage detector. In this device, the correlation function is determined by signals from vibration detectors positioned on either side of the water leakage location at parts that are exposed above ground, such as fire hydrants, sluice valves, water meters, etc. The distance to the position of water leakage can be ascertained by finding the phase lag time of the two signals for which the correlation coefficient is a maximum and multiplying that lag time by the phase speed of vibrations in the pipe.
Problems exist, however, with the above described two methods. With respect to the sound-picked method, that method depends on the personal abilities of the individual skilled worker, and in the correlation method, not only must the vibration detectors be positioned at two locations, but also the mutual correlation coefficient must be calculated in real time. Thus, the correlation method requires relatively bulky equipment for operation.